Zkittlez OG Auto

Are you sure you want to only do 3? You could easily do for example 6 in that space. I use everything between 10-20L, 15L is quite a sweet spot for most strains. A 8 week strain will not properly fill a 20L pot, but you don't get full potential of a 15 week strain in a 10L either. Too big can be hard to manage with watering and the smaller it is the more often you need to water and it can limit how big the plant can get. If you get 15L pots they'll do fine with basically any autoflower.